iemejia commented on code in PR #3855:
URL: https://github.com/apache/avro/pull/3855#discussion_r3567388063
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lang/perl/lib/Avro/DataFileReader.pm:
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@@ -207,32 +212,156 @@ sub read_block_header {
return if $codec eq 'null';
- ## we need to read the entire block into memory, to inflate it
- my $nread = read $fh, my $block, $datafile->{block_size} + MARKER_SIZE
- or croak "Error reading from file: $!";
+ ## Guard against an attacker-controlled block_size triggering a huge
+ ## allocation for the compressed block itself, before any decompression
+ ## happens. When the reader is configured with block_max_size, reject a
+ ## block whose declared compressed size exceeds that bound up front.
+ my $block_max = $datafile->{block_max_size};
+ if (defined $block_max && $datafile->{block_size} > $block_max) {
+ Avro::DataFile::Error::CompressedBlockSize->throw(
+ "Compressed block size $datafile->{block_size} exceeds the
configured block_max_size of $block_max bytes"
Review Comment:
Perl does interpolate a hash-element deref like `$datafile->{block_size}`
inside a double-quoted string (verified: it prints the value, e.g. `1234`, not
`HASH(0x...)`), so the message was already correct. I've extracted a
`$block_size` local and used it in both the comparison and the message for
clarity.
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